Mohammed al-Taluli's family said Monday the 25-year-old was detained by Hamas after posting a video on YouTube in which he accused the group of "pushing the youths to death" to stay in power.
For weeks, Palestinians have rallied at the Gaza fence against the deteriorating living conditions in the impoverished coastal territory, which has been under an Israeli and Egyptian blockade since Hamas took over in 2007. Youths have thrown rocks at Israeli soldiers, and two Palestinians have been killed in the clashes.
Al-Taluli and his friends have been detained by Hamas several times since organizing protests in January against power cuts.
Gaza's militant Hamas rulers warned of on Monday of renewed violence if Israel acquiesces to Palestinian President Mahmoud Abbas' wishes and reduces its electricity supply to the isolated territory.
Gaza's 2 million residents already get by with only four hours of electricity a day. In an effort to push his Hamas rivals out of power, Abbas says his West Bank government will stop paying Israel to provide electricity.
That has put Israel in the tough spot of having to choose between siding with Hamas in the internal Palestinian struggle or risking a humanitarian crisis in the impoverished coastal strip.